One of California’s foremost experts on freshwater fish believes there may be hope for restoring native salmon to abundance – but there’s a catch: California must build the controversial Delta tunnels, he says.

“The expected costs are tremendous and there is a lot of concern over that, but our paper is about what’s good for fish,” said Peter Moyle, a professor of fisheries with the University of California, Davis Center for Watershed Sciences. “Will the Delta tunnels be good for fish or not? I think they will.”

Moyle co-authored a 63-page report with colleagues John Durand and Carson Jeffres that was released on Tuesday. It proposes a comprehensive game plan for restoring the Sacramento-San Joaquin Delta and saving native fish from extinction. Achieving this goal, according to the report, will require restoring a great deal of riverside habitat in the northern and western Delta. Saving the native fish, the report says, will also probably require building the Delta tunnels, or something resembling them.

The tunnels, known officially as California WaterFix, would create a new conveyance system under the delta at an estimated cost of $17 billion. Such an alternative water diversion system, the authors explain in their paper, could help alleviate strains on the Delta currently caused by powerful water pumps at the south edge of the estuary, as long it is coupled with large-scale habitat restoration projects.

The paper was commissioned by Orange County Coastkeeper, which received guidance and direction in the effort by the Municipal Water District (MWD) of Orange County, according to meeting reports from late 2016 and early 2017. Garry Brown, the executive director of Orange County Coastkeeper, said his organization funded the paper and that no funding came from water agencies.

But Barbara Barrigan-Parrilla, executive director of the group Restore the Delta, which opposes the tunnel project, believes the paper’s findings were influenced by the MWD. The district receives water from the Delta via the State Water Project and potentially has much to gain from the tunnels, which its supporters say will improve the consistency and reliability of deliveries.

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